14 Shufeldt, Osteology of Orthorhamphus magnirostris. [.^fXiy 



The Pectoral Arch. — All the bones composing this part of the 

 skeleton in Orthorhamphus are strongly developed and of con- 

 spicuous size (iig. 8, Plate III., and figs. 9 and 10, Plate IV.) 



When articulated, as in life, the scapitlce extend several milli- 

 meters posterior to the anterior hmits of the iha of the pelvis ; 

 a coracoid exceeds in length half of the longitudinal axis of the 

 body of the sternum ; and the broad, U-shaped as fiircitla, with 

 its small, peg-like hypocleidium, is, comparatively speaking, much 

 stronger than it is in certain Laridce possessing a trunk skeleton 

 of proportions equalhng that of the present subject. 



Below, the os furculum stands well away from the anterior 

 margin of the sternum, being separated by at least a centimeter. 

 Mesially, below, this bone is compressed from before, backwards, 

 while the clavicular limbs above are flattened transversely. 

 Superiorly, the distal end, on either side, makes a substantial 

 articulation with the scapula, and a very extensive one with the 

 head of the corresponding coracoid as it passes it. Thus, it will 

 be seen that the formation of the foramen triosseiim is very com- 

 plete in Orthorhamphus. 



As in Plovers and Gulls, but not in Oyster-catchers, the coracoids 

 are separated from each other in their sternal grooves or beds 

 by the posterior portion of the manubrium. At its lower part, 

 either one of these bones is much compressed from before, back- 

 wards, and much expanded transversely. Both externally and 

 mesially on this expanded portion below, there is developed an 

 apophysis which, in either case, is directed upwards, almost 

 parallel to the longitudinal axis of the bone. Of these two 

 processes, the outer one is the larger, and is constantly present. 

 The inner one appears to be an ossification of the ligament which 

 is attached at the infero-mesial angle of the coracoid, and con- 

 sequently may or may not be present, depending on the age of 

 the individual. Indeed, as Dr. Gadow remarks, the " configura- 

 tion of the various processes of these bones is manifold, and of 

 great taxonomic importance, as has been exhaustively shown by 

 Professor Flirbringer, in whose Uniersuchungen zitr Morphologic 

 mid Systematik der Vogel about one hundred figures of this articula- 

 tion in different birds are given.* 



The precoracoidal process extends nearly half-way down the 

 shaft, and is pierced below by the foramen for the supracoracoidal 

 nerve, as in the Strigida and some other birds, as many Liiiiicolcs 

 and Laridce. 



For its anterior moiety a scapula is somewhat narrow and thick, 

 being broader, with a thin, truncate blade behind, the whole bone 

 having a cimeter-form, with sharp edges for its posterior third. 

 Anteriorly it makes an extensive and close articulation with the 

 coracoid, and is, on either side, in contact with the free posterior 

 extremity of the clavicular arch or os fnrciiliun. 



* Gadow, Hans, Newton's " Diet, of Birds," p. S56. In the ligures given 

 here, the lettering is incorrect, in so far as the pectoral arch of Bubo ignavus 

 is concerned, as Acd is made to indicate the scapula instead of the letters Sc. 



